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At the earliest moments of the Universe, there were no separate forces, energy or matter. It was all just the same stuff. And then the different forces froze out, differentiating into electromagnetism, the strong force and the weak force. Today we’ll look at the problem that has puzzled physicists for generations: is there a single equation that explains all the forces we see in the Universe. Is there a theory of everything?
After a quick Dragon*Con break, we’re back to our tour through the fundamental forces of the Universe. We’ve covered gravity and electromagnetism, and now we’re moving onto the strong and weak nuclear forces. We didn’t think they’d really need to be separate episodes, so we’re putting them together. And then we’ll cap the whole series with the quest for the theory of everything.
I apologize that Universe Today has been a little slow over the last couple of days. That’s because my webserver is completely bogged down with Google searchers worried that the world is going to end thanks to the Large Hadron Collider.
Don’t worry, it’s not. In fact, the twin proton beams fired for the first time today. Since you’re reading this, the Universe wasn’t torn apart.
But let’s just say that the Large Hadron Collider does create a microscopic black hole? What then… are we doomed? Nope. Ethan Seigel over at Starts With a Bang has done the calculations to figure out how massive a black hole would be created, and how much of the Earth it would consume if it fell down into the planet. He also calculates how long it should last before evaporating away. There you go, you can use these calculations to help your panicked friends realize there’s no need to worry about microscopic black holes.
And in a strange twist of irony, Google has changed today’s logo to celebrate the Large Hadron Collider. At least, that’s what I’m seeing here in Canada. Google's LHC logo
We don’t mean to beat a dead horse – both Fraser and Ian have already covered this topic quite thoroughly — but just in case anyone still has any fears about the Large Hadron Collider meaning the end of the world, a new report published today provides the most comprehensive evidence available to confirm that the LHC’s switch-on, due on Wednesday next week, poses no threat to mankind. A copy of the report is available HERE. In a nutshell, it says nature’s own cosmic rays regularly produce more powerful particle collisions than those planned within the LHC, and nothing bad has happened to Earth from those quite natural and frequent events. The LHC will be studying nature’s laws in controlled experiments. So just relax and watch the LHC rap video.
The LHC Safety Assessment Group have reviewed and updated a study first completed in 2003, which dispels fears of universe-gobbling black holes and of other possibly dangerous new forms of matter, and confirms that the switch-on will be completely safe.
The report, ‘Review of the Safety of LHC Collisions’, published in IOP Publishing’s Journal of Physics G: Nuclear and Particle Physics, proves that if particle collisions at the LHC had the power to destroy the Earth, we would never have been given the chance to exist, because regular interactions with more energetic cosmic rays would already have destroyed the Earth or other astronomical bodies.
The Safety Assessment Group compares the rates of cosmic rays that bombard Earth, other planets in our solar system, the Sun and all the other stars in our universe itself to show that hypothetical black holes or strangelets, that have raised fears in some, will in fact pose no threat.
The report also concludes that, since cosmic-ray collisions are more energetic than those in the LHC, but are incapable of producing vacuum bubbles or dangerous magnetic monopoles, we should not fear their creation by the LHC.
LHC collisions will differ from cosmic-ray collisions in that any exotic particles created will have lower velocities, but the Safety Assessment Group shows that even fast-moving black holes produced by cosmic rays would have stopped inside the Earth or other astronomical bodies. Their existence proves that any such black holes could not gobble matter at a risky rate.
As the Safety Assessment Group writes, “Each collision of a pair of protons in the LHC will release an amount of energy comparable to that of two colliding mosquitoes, so any black hole produced would be much smaller than those known to astrophysicists.” They conclude that such microscopic black holes could not grow dangerously.
As for the equally hypothetical strangelets, the review uses recent experimental measurements at the Brookhaven National Laboratory’s Relativistic Heavy-Ion Collider, New York, to prove that they will not be produced during collisions in the LHC.
One gigabyte per second? No problem. The LHC computing grid could revolutionize how we handle data over Internet (CERN)
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We already know that the Large Hadron Collider (LHC) will be the biggest, most expensive physics experiment ever carried out by mankind. Colliding relativistic particles at energies previously unimaginable (up to the 14 TeV mark by the end of the decade) will generate millions of particles (known and as yet to be discovered), that need to be tracked and characterized by huge particle detectors. This historic experiment will require a massive data collection and storage effort, re-writing the rules of data handling. Every five seconds, LHC collisions will generate the equivalent of a DVD-worth of data, that’s a data production rate of one gigabyte per second. To put this into perspective, an average household computer with a very good connection may be able to download data at a rate of one or two megabytes per second (if you are very lucky! I get 500 kilobytes/second). So, LHC engineers have designed a new kind of data handling method that can store and distribute petabytes (million-gigabytes) of data to LHC collaborators worldwide (without getting old and grey whilst waiting for a download).
In 1990, the European Organization for Nuclear Research (CERN) revolutionized the way in which we live. The previous year, Tim Berners-Lee, a CERN physicist, wrote a proposal for electronic information management. He put forward the idea that information could be transferred easily over the Internet using something called “hypertext.” As time went on Berners-Lee and collaborator Robert Cailliau, a systems engineer also at CERN, pieced together a single information network to help CERN scientists collaborate and share information from their personal computers without having to save it on cumbersome storage devices. Hypertext enabled users to browse and share text via web pages using hyperlinks. Berners-Lee then went on to create a browser-editor and soon realised this new form of communication could be shared by vast numbers of people. By May 1990, the CERN scientists called this new collaborative network the World Wide Web. In fact, CERN was responsible for the world’s first website: http://info.cern.ch/ and an early example of what this site looked like can be found via the World Wide Web Consortium website.
So CERN is no stranger to managing data over the Internet, but the brand new LHC will require special treatment. As highlighted by David Bader, executive director of high performance computing at the Georgia Institute of Technology, the current bandwidth allowed by the Internet is a huge bottleneck, making other forms of data sharing more desirable. “If I look at the LHC and what it’s doing for the future, the one thing that the Web hasn’t been able to do is manage a phenomenal wealth of data,” he said, meaning that it is easier to save large datasets on terabyte hard drives and then send them in the post to collaborators. Although CERN had addressed the collaborative nature of data sharing on the World Wide Web, the data the LHC will generate will easily overload the small bandwidths currently available.
How the LHC Computing Grid works (CERN/Scientific American)
This is why the LHC Computing Grid was designed. The grid handles vast LHC dataset production in tiers, the first (Tier 0) is located on-site at CERN near Geneva, Switzerland. Tier 0 consists of a huge parallel computer network containing 100,000 advanced CPUs that have been set up to immediately store and manage the raw data (1s and 0s of binary code) pumped out by the LHC. It is worth noting at this point, that not all the particle collisions will be detected by the sensors, only a very small fraction can be captured. Although only a comparatively small number of particles may be detected, this still translates into huge output.
Tier 0 manages portions of the data outputted by blasting it through dedicated 10 gigabit-per-second fibre optic lines to 11 Tier 1 sites across North America, Asia and Europe. This allows collaborators such as the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory in New York to analyse data from the ALICE experiment, comparing results from the LHC lead ion collisions with their own heavy ion collision results.
From the Tier 1 international computers, datasets are packaged and sent to 140 Tier 2 computer networks located at universities, laboratories and private companies around the world. It is at this point that scientists will have access to the datasets to perform the conversion from the raw binary code into usable information about particle energies and trajectories.
The tier system is all well and good, but it wouldn’t work without a highly efficient type of software called “middleware.” When trying to access data, the user may want information that is spread throughout the petabytes of data on different servers in different formats. An open-source middleware platform called Globus will have the huge responsibility to gather the required information seamlessly as if that information is already sitting inside the researcher’s computer.
It is this combination of the tier system, fast connection and ingenious software that could be expanded beyond the LHC project. In a world where everything is becoming “on demand,” this kind of technology could make the Internet transparent to the end user. There would be instant access to everything from data produced by experiments on the other side of the planet, to viewing high definition movies without waiting for the download progress bar. Much like Berners-Lee’s invention of HTML, the LHC Computing Grid may revolutionize how we use the Internet.
Puzzled about particle physics? Want to know what the inside of the Large Hadron Collider looks like? Like music, fun and science? Want to know for sure the LHC won’t create a black hole that will swallow the Earth? Find all of the above in a rap song created by Kate McAlpine, 23, who used to work in the press office of CERN, where on September 10, the LHC will be powered up. The song has been a hit on You Tube, and has been downloaded over 400,000 times. Physicists say the science in the song is “spot on” and provides a rhythmic tour of the mysteries of modern physics and the workings of the LHC, while noting that “the things that it discovers will rock you in the head.” Without further ado, here it is:
McAlpine wrote the rap during her 40-minute morning commute to CERN. “Some more academic people are not too happy and they think it kind of cheapens the science and dumbs it down,” she says. “But I think mostly people are excited to have this rap out there. And a lot of people at CERN just think it’s great, so that’s exciting.”
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We’ve all wondered at some point or another what mysteries our Solar System holds. After all, the eight planets (plus Pluto and all those other dwarf planets) orbit within a very small volume of the heliosphere (the volume of space dominated by the influence of the Sun), what’s going on in the rest of the volume we call our home? As we push more robots into space, improve our observational capabilities and begin to experience space for ourselves, we learn more and more about the nature of where we come from and how the planets have evolved. But even with our advancing knowledge, we would be naive to think we have all the answers, so much still needs to be uncovered. So, from a personal point of view, what would I consider to be the greatest mysteries within our Solar System? Well, I’m going to tell you my top ten favourites of some more perplexing conundrums our Solar System has thrown at us. So, to get the ball rolling, I’ll start in the middle, with the Sun. (None of the following can be explained by dark matter, in case you were wondering… actually it might, but only a little…)
10. Solar Pole Temperature Mismatch
Data from Ulysses (D. McComas)
Why is the Sun’s South Pole cooler than the North Pole? For 17 years, the solar probe Ulysses has given us an unprecedented view of the Sun. After being launched on Space Shuttle Discovery way back in 1990, the intrepid explorer took an unorthodox trip through the Solar System. Using Jupiter for a gravitational slingshot, Ulysses was flung out of the ecliptic plane so it could pass over the Sun in a polar orbit (spacecraft and the planets normally orbit around the Sun’s equator). This is where the probe journeyed for nearly two decades, taking unprecedented in-situ observations of the solar wind and revealing the true nature of what happens at the poles of our star. Alas, Ulysses is dying of old age, and the mission effectively ended on July 1st (although some communication with the craft remains).
However, observing uncharted regions of the Sun can create baffling results. One such mystery result is that the South Pole of the Sun is cooler than the North Pole by 80,000 Kelvin. Scientists are confused by this discrepancy as the effect appears to be independent of the magnetic polarity of the Sun (which flips magnetic north to magnetic south every 11-years). Ulysses was able to gauge the solar temperature by sampling the ions in the solar wind at a distance of 300 million km above the North and South Poles. By measuring the ratio of oxygen ions (O6+/O7+), the plasma conditions at the base of the coronal hole could be measured.
Mars, just a normal planet. No mystery here... (NASA/Hubble)
Why are the Martian hemispheres so radically different? This is one mystery that had frustrated scientists for years. The northern hemisphere of Mars is predominantly featureless lowlands, whereas the southern hemisphere is stuffed with mountain ranges, creating vast highlands. Very early on in the study of Mars, the theory that the planet had been hit by something very large (thus creating the vast lowlands, or a huge impact basin) was thrown out. This was primarily because the lowlands didn’t feature the geography of an impact crater. For a start there is no crater “rim.” Plus the impact zone is not circular. All this pointed to some other explanation. But eagle-eyed researchers at Caltech have recently revisited the impactor theory and calculated that a huge rock between 1,600 to 2,700 km diameter can create the lowlands of the northern hemisphere (see Two Faces of Mars Explained).
Bonus mystery: Does the Mars Curse exist? According to many shows, websites and books there is something (almost paranormal) out in space eating (or tampering with) our robotic Mars explorers. If you look at the statistics, you would be forgiven for being a little shocked: Nearly two-thirds of all Mars missions have failed. Russian Mars-bound rockets have blown up, US satellites have died mid-flight, British landers have pock-marked the Red Planet’s landscape; no Mars mission is immune to the “Mars Triangle.” So is there a “Galactic Ghoul” out there messing with our ‘bots? Although this might be attractive to some of us superstitious folk, the vast majority of spacecraft lost due to The Mars Curse is mainly due to heavy losses during the pioneering missions to Mars. The recent loss rate is comparable to the losses sustained when exploring other planets in the Solar System. Although luck may have a small part to play, this mystery is more of a superstition than anything measurable (see The “Mars Curse”: Why Have So Many Missions Failed?).
8. The Tunguska Event
Artist impression of the Tunguska event (www.russianspy.org)
What caused the Tunguska impact? Forget Fox Mulder tripping through the Russian forests, this isn’t an X-Files episode. In 1908, the Solar System threw something at us… but we don’t know what. This has been an enduring mystery ever since eye witnesses described a bright flash (that could be seen hundreds of miles away) over the Podkamennaya Tunguska River in Russia. On investigation, a huge area had been decimated; some 80 million trees had been felled like match sticks and over 2,000 square kilometres had been flattened. But there was no crater. What had fallen from the sky?
This mystery is still an open case, although researchers are pinning their bets of some form of “airburst” when a comet or meteorite entered the atmosphere, exploding above the ground. A recent cosmic forensic study retraced the steps of a possible asteroid fragment in the hope of finding its origin and perhaps even finding the parent asteroid. They have their suspects, but the intriguing thing is, there is next-to-no meteorite evidence around the impact site. So far, there doesn’t appear to be much explanation for that, but I don’t think Mulder and Scully need be involved (see Tunguska Meteoroid’s Cousins Found?).
7. Uranus’ Tilt
Uranus. Does it on its side (NASA/Hubble)
Why does Uranus rotate on its side? Strange planet is Uranus. Whilst all the other planets in the Solar System more-or-less have their axis of rotation pointing “up” from the ecliptic plane, Uranus is lying on its side, with an axial tilt of 98 degrees. This means that for very long periods (42 years at a time) either its North or South Pole points directly at the Sun. The majority of the planets have a “prograde” rotation; all the planets rotate counter-clockwise when viewed from above the Solar System (i.e. above the North Pole of the Earth). However, Venus does the exact opposite, it has a retrograde rotation, leading to the theory that it was kicked off-axis early in its evolution due to a large impact. So did this happen to Uranus too? Was it hit by a massive body?
Some scientists believe that Uranus was the victim of a cosmic hit-and-run, but others believe there may be a more elegant way of describing the gas giant’s strange configuration. Early in the evolution of the Solar System, astrophysicists have run simulations that show the orbital configuration of Jupiter and Saturn may have crossed a 1:2 orbital resonance. During this period of planetary upset, the combined gravitational influence of Jupiter and Saturn transferred orbital momentum to the smaller gas giant Uranus, knocking it off-axis. More research needs to be carried out to see if it was more likely that an Earth-sized rock impacted Uranus or whether Jupiter and Saturn are to blame.
6. Titan’s Atmosphere
False colour image of Titan's atmosphere. Credit: NASA/JPL/Space Science Institute/ESA
Why does Titan have an atmosphere? Titan, one of Saturn’s moons, is the only moon in the Solar System with a significant atmosphere. It is the second biggest moon in the Solar System (second only to Jupiter’s moon Ganymede) and about 80% more massive than Earth’s Moon. Although small when compared with terrestrial standards, it is more Earth-like than we give it credit for. Mars and Venus are often cited as Earth’s siblings, but their atmospheres are 100 times thinner and 100 times thicker, respectively. Titan’s atmosphere on the other hand is only one and a half times thicker than Earth’s, plus it is mainly composed of nitrogen. Nitrogen dominates Earth’s atmosphere (at 80% composition) and it dominates Titans atmosphere (at 95% composition). But where did all this nitrogen come from? Like on Earth, it’s a mystery.
Titan is such an interesting moon and is fast becoming the prime target to search for life. Not only does it have a thick atmosphere, its surface is crammed full with hydrocarbons thought to be teeming with “tholins,” or prebiotic chemicals. Add to this the electrical activity in the Titan atmosphere and we have an incredible moon with a massive potential for life to evolve. But as to where its atmosphere came from… we just do not know.
5. Solar Coronal Heating
Coronal loops as imaged by TRACE at 171 Angstroms (1 million deg C) (NASA/TRACE)
Why is the solar atmosphere hotter than the solar surface? Now this is a question that has foxed solar physicists for over half a century. Early spectroscopic observations of the solar corona revealed something perplexing: The Sun’s atmosphere is hotter than the photosphere. In fact, it is so hot that it is comparable to the temperatures found in the core of the Sun. But how can this happen? If you switch on a light bulb, the air surrounding the glass bulb wont be hotter than the glass itself; as you get closer to a heat source, it gets warmer, not cooler. But this is exactly what the Sun is doing, the solar photosphere has a temperature of around 6000 Kelvin whereas the plasma only a few thousand kilometres above the photosphere is over 1 million Kelvin. As you can tell, all kinds of physics laws appear to be violated.
However, solar physicists are gradually closing in on what may be causing this mysterious coronal heating. As observational techniques improve and theoretical models become more sophisticated, the solar atmosphere can be studied more in-depth than ever before. It is now believed that the coronal heating mechanism may be a combination of magnetic effects in the solar atmosphere. There are two prime candidates for corona heating: nanoflares and wave heating. I for one have always been a huge advocate of wave heating theories (a large part of my research was devoted to simulating magnetohydrodynamic wave interactions along coronal loops), but there is strong evidence that nanoflares influence coronal heating too, possibly working in tandem with wave heating.
Although we are pretty certain that wave heating and/or nanoflares may be responsible, until we can insert a probe deep into the solar corona (which is currently being planned with the Solar Probe mission), taking in-situ measurements of the coronal environment, we won’t know for sure what heats the corona (see Warm Coronal Loops May Hold the Key to Hot Solar Atmosphere).
4. Comet Dust
Comets - where does their dust come from?
How did dust formed at intense temperatures appear in frozen comets? Comets are the icy, dusty nomads of the Solar System. Thought to have evolved in the outermost reaches of space, in the Kuiper Belt (around the orbit of Pluto) or in a mysterious region called the Oort Cloud, these bodies occasionally get knocked and fall under the weak gravitational pull of the Sun. As they fall toward the inner Solar System, the Sun’s heat will cause the ice to vaporize, creating a cometary tail known as the coma. Many comets fall straight into the Sun, but others are more lucky, completing a short-period (if they originated in the Kuiper Belt) or long-period (if they originated in the Oort Cloud) orbit of the Sun.
But something odd has been found in the dust collected by NASA’s 2004 Stardust mission to Comet Wild-2. Dust grains from this frozen body appeared to have been formed a high temperatures. Comet Wild-2 is believed to have originated from and evolved in the Kuiper Belt, so how could these tiny samples be formed in an environment with a temperature of over 1000 Kelvin?
The Solar System evolved from a nebula some 4.6 billion years ago and formed a large accretion disk as it cooled. The samples collected from Wild-2 could only have been formed in the central region of the accretion disk, near the young Sun, and something transported them into the far reaches of the Solar System, eventually ending up in the Kuiper Belt. But what mechanism could do this? We are not too sure (see Comet Dust is Very Similar to Asteroids).
3. The Kuiper Cliff
The bodies in the Kuiper Belt (Don Dixon)
Why does the Kuiper Belt suddenly end? The Kuiper Belt is a huge region of the Solar System forming a ring around the Sun just beyond the orbit of Neptune. It is much like the asteroid belt between Mars and Jupiter, the Kuiper Belt contains millions of small rocky and metallic bodies, but it’s 200-times more massive. It also contains a large quantity of water, methane and ammonia ices, the constituents of cometary nuclei originating from there (see #4 above). The Kuiper Belt is also known for its dwarf planet occupant, Pluto and (more recently) fellow Plutoid “Makemake”.
The Kuiper Belt is already a pretty unexplored region of the Solar System as it is (we wait impatiently for NASA’s New Horizons Pluto mission to arrive there in 2015), but it has already thrown up something of a puzzle. The population of Kuiper Belt Objects (KBOs) suddenly drops off at a distance of 50 AU from the Sun. This is rather odd as theoretical models predict an increase in number of KBOs beyond this point. The drop-off is so dramatic that this feature has been dubbed the “Kuiper Cliff.”
We currently have no explanation for the Kuiper Cliff, but there are some theories. One idea is that there are indeed a lot of KBOs beyond 50 AU, it’s just that they haven’t accreted to form larger objects for some reason (and therefore cannot be observed). Another more controversial idea is that KBOs beyond the Kuiper Cliff have been swept away by a planetary body, possibly the size of Earth or Mars. Many astronomers argue against this citing a lack of observational evidence of something that big orbiting outside the Kuiper Belt. This planetary theory however has been very useful for the doomsayers out there, providing flimsy “evidence” for the existence of Nibiru, or “Planet X.” If there is a planet out there, it certainly is not “incoming mail” and it certainly is notarriving on our doorstep in 2012.
So, in short, we have no clue why the Kuiper Cliff exists…
2. The Pioneer Anomaly
Artist impression of the Pioneer 10 probe (NASA)
Why are the Pioneer probes drifting off-course? Now this is a perplexing issue for astrophysicists, and probably the most difficult question to answer in Solar System observations. Pioneer 10 and 11 were launched back in 1972 and 1973 to explore the outer reaches of the Solar System. Along their way, NASA scientists noticed that both probes were experiencing something rather strange; they were experiencing an unexpected Sun-ward acceleration, pushing them off-course. Although this deviation wasn’t huge by astronomical standards (386,000 km off course after 10 billion km of travel), it was a deviation all the same and astrophysicists are at a loss to explain what is going on.
One main theory suspects that non-uniform infrared radiation around the probes’ bodywork (from the radioactive isotope of plutonium in its Radioisotope Thermoelectric Generators) may be emitting photons preferentially on one side, giving a small push toward the Sun. Other theories are a little more exotic. Perhaps Einstein’s general relativity needs to be modified for long treks into deep space? Or perhaps dark matter has a part to play, having a slowing effect on the Pioneer spacecraft?
How do we know the Oort Cloud even exists? As far as Solar System mysteries go, the Pioneer anomaly is a tough act to follow, but the Oort cloud (in my view) is the biggest mystery of all. Why? We have never seen it, it is a hypothetical region of space.
At least with the Kuiper Belt, we can observe the large KBOs and we know where it is, but the Oort Cloud is too far away (if it really is out there). Firstly, the Oort Cloud is predicted to be over 50,000 AU from the Sun (that’s nearly a light year away), making it about 25% of the way toward our nearest stellar neighbour, Proxima Centauri. The Oort Cloud is therefore a very long way away. The outer reaches of the Oort Cloud is pretty much the edge of the Solar System, and at this distance, the billions of Oort Cloud objects are very loosely gravitationally bound to the Sun. They can therefore be dramatically influenced by the passage of other nearby stars. It is thought that Oort Cloud disruption can lead to icy bodies falling inward periodically, creating long-period comets (such as Halley’s comet).
In fact, this is the only reason why astronomers believe the Oort Cloud exists, it is the source of long-period icy comets which have highly eccentric orbits emanating regions out of the ecliptic plane. This also suggests that the cloud surrounds the Solar System and is not confined to a belt around the ecliptic.
So, the Oort Cloud appears to be out there, but we cannot directly observe it. In my books, that is the biggest mystery in the outermost region of our Solar System…
Rendering of a blue liquid metal... could this be what metallic helium looks like? Source: http://tinyurl.com/6lffol (waxellis)
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The interiors of the two gas giants, Jupiter and Saturn, are pretty extreme places. With atmospheric pressures of around 70 million Earth atmospheres, the phases of material become a bit difficult to understand. Usually when we think of a liquid metal, we have thoughts about liquid mercury at room temperature (or the reassembling liquid metal T-1000 played by Robert Patrick in the film Terminator 2), rarely do we consider two of the most abundant elements in the Universe to be a liquid metal in certain conditions. And yet, this is what a team of physicists from UC Berkley are claiming; helium and hydrogen can mix together, forced by the massive pressures near the cores of Jupiter and Saturn, forming a liquid metal alloy, possibly changing our perception of what lies beneath those Jovian storms…
Usually planetary physicists and chemists focus most of their attention on the characteristics of the most abundant element in the Universe: hydrogen. Indeed, over 90% of both Jupiter and Saturn is hydrogen too. But within these gas giant’s atmospheres is not the simple hydrogen atom, it is the surprisingly complex diatomic hydrogen gas (i.e. molecular hydrogen, H2). So, to understand the dynamics and nature of the insides of the most massive planets in our Solar System, researchers from UC Berkley and London are looking into a far simpler element; the second most abundant gas in the Universe: helium.
Raymond Jeanloz, a professor at UC Berkeley, and his team have uncovered an interesting characteristic of helium at the extreme pressures that can be exerted near the cores of Jupiter and Saturn. Helium will form a metallic liquid alloy when mixed with hydrogen. This state of matter was thought to be rare, but these new findings suggest liquid metal helium alloys may be more common than we previously thought.
“This is a breakthrough in terms of our understanding of materials, and that’s important because in order to understand the long-term evolution of planets, we need to know more about their properties deep down. The finding is also interesting from the point of view of understanding why materials are the way they are, and what determines their stability and their physical and chemical properties.” – Raymond Jeanloz.
Jupiter for example exerts an enormous pressure on the gases in its atmosphere. Due to it’s large mass, one can expect pressures up to 70 million Earth atmospheres (no, that isn’t enough to kick-start fusion…), creating core temperatures of between 10,000 to 20,000 K (that’s 2-4 times hotter than the Sun’s photosphere!). So helium was chosen as the element to study under these extreme conditions, a gas that makes up 5-10% of the Universe’s observable matter.
Using quantum mechanics to calculate the behaviour of helium under different extreme pressures and temperatures, the researchers found that helium will turn into a liquid metal at very high pressure. Usually, helium is thought of as a colourless and transparent gas. In Earth-atmosphere conditions this is true. However, it turns into an entirely different creature at 70 million Earth atmospheres. Rather than being an insulating gas, it turns into a conducting liquid metal substance, more like mercury, “only less reflective,” Jeanloz added.
This result comes as a surprise as it has always been thought that massive pressures make it more difficult for elements like hydrogen and helium to become metal-like. This is because the high temperatures in locations like Jupiter’s core cause increased vibrations in atoms, thus deflecting the paths of electrons trying to flow in the material. If there is no electron flow, the material becomes an insulator and cannot be called a “metal.”
However, these new findings suggest that atomic vibrations under these kinds of pressures actually have the counter-intuitive effect of creating new paths for the electrons to flow. Suddenly the liquid helium becomes conductive, meaning it is a metal.
In another twist, it is thought that the helium liquid metal could easily mix with hydrogen. Planetary physics tells us that this isn’t possible, hydrogen and helium separate like oil and water inside the gas giant bodies. But Jeanloz’s team has found that the two elements could actually mix, creating a liquid metal alloy. If this is to be the case, some serious re-thinking of planetary evolution needs to be done.
Both Jupiter and Saturn release more energy than the Sun provides meaning both planets are generating their own energy. The accepted mechanism for this is condensing helium droplets that fall from the planets’ upper atmospheres and to the core, releasing gravitational potential as the helium falls as “rain.” However, if this research is proven to be the case, the gas giant interior is likely to be a lot more homogenous than previously thought meaning there can be no helium droplets.
So the next task for Jeanloz and his team is to find an alternate power source generating heat in the cores of Jupiter and Saturn (so don’t go re-writing the textbooks quite yet…)
A series of problems forced LHC shutdown (CERN/LHC)
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It’s official, the Large Hadron Collider (LHC) will begin operations in a little over a month. On September 10th, the most sophisticated particle accelerator will go online, injecting the first circulation of accelerated particles. Actual experiments involving collisions will occur once scientists are satisfied the LHC is fully optimized and calibration is complete. The LHC has been undergoing “cool-down” for some time, ensuring the LHC’s eight sectors are approaching the 1.9K (-271°C) operational temperature (that is 1.9 degrees above absolute zero). All going well, on September 10th, the first beam will be accelerated to an energy of 450 GeV (0.45 TeV), the preliminary step on the path to attaining particle energies of 5 TeV, a record breaking target… awesome.
Earlier today, CERN announced that the LHC will be ready by September 10th to attempt to circulate a beam of particles. This news comes as the “cool-down” phase of LHC commissioning reaches a successful conclusion, cooling all eight sectors to 1.9 degrees above absolute zero. To manage temperatures this extreme has been a long and painstaking task, referred to as a “marathon” by the project leader:
“We’re finishing a marathon with a sprint. It’s been a long haul, and we’re all eager to get the LHC research programme underway.” – LHC project leader Lyn Evans.
Now scientists and engineers must synchronize the LHC with the Super Proton Synchrotron (SPS) accelerator, which is the last component in the LHC’s particle injector chain. For the system to work, the LHC and SPS must be synchronized to within a fraction of a nanosecond. This task is expected to begin on August 9th (Saturday). These calibration tasks are expected to continue through August and into the beginning of September, preparing the LHC for its first particle injection on the 10th.
The LHC will accelerate particles to relativistic velocities, accessing energies previously unimaginable. Once the LHC reaches its optimum design specification (possibly by 2010), it will generate beams seven-times more energetic and 30-times more intense than any other particle accelerator on the planet. The accelerator ring lies below the Swiss countryside with a circumference of 27 km (17 miles).
The heliopause is the frontier between the Solar System and the interstellar medium. Credit: NASA/JPL
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Space is far from empty. The Solar System can be viewed as a “bubble” of solar matter – filled with particles emitted by the Sun as the solar wind – extending well beyond the orbit of Pluto. The solar wind velocity is supersonic for most of this distance (exceeding a million miles per hour), but the point at which it begins to interact with the interstellar medium (ISM), the solar wind drops to subsonic velocities, creating a region of compression known as the termination shock. After 26 years of flight, the Voyager 1 deep space probe entered this bizarre, turbulent region of space, where solar particles build up and magnetic fields become twisted. Now a new mission has been designed to watch this region of space from afar to begin to understand the boundary of our solar system, where violent turbulence rules and high-energy atoms are generated…
In 2004, Voyager 1 hit it and in 2006, Voyager 2 hit it. The first probe flew through the termination shock at around 94 AU (8 billion miles away); the second measured it at only 76 AU (7 billion miles). This result alone suggests that the termination shock may be irregularly shaped and/or variable depending on solar activity. Before the Voyager missions, the termination shock was theorized, but there was little observational evidence until the two veteran probes traversed the region. The termination shock is of paramount importance to understanding the nature of the outer reaches of the solar system as, counter-intuitively, the Sun’s activity increases, the region beyond the termination shock (the heliosheath) becomes more efficient at blocking deadly cosmic rays. During solar minimum, it becomes less efficient at blocking cosmic rays.
Artist impression of Voyager 1, the first probe to traverse the heliosheath (NASA)
In an effort to map the location and characteristics of the termination shock and heliosheath beyond, NASA scientists are preparing the Interstellar Boundary Explorer (IBEX) for launch in October. IBEX is part of NASA’s Small Explorer program (SMEX), where inexpensive, small probes are used to efficiently observe particular cosmic phenomena. IBEX will be orbiting beyond the influence of the Earth’s magnetic field (the magnetosphere) at a 200,000 mile distance from the Earth. This is because the phenomenon IBEX will be observing can be generated by our own magnetic field. So what will IBEX be measuring? To understand the interaction between solar wind ions and the interstellar medium, IBEX will use two sensors to detect energetic neutral atoms (ENAs) being blasted from the outermost reaches of the solar system.
How are ENAs generated and how are they a measurement of the interaction between the heliosphere and the ISM? Out there in the ISM exists neutral atoms and ions. As the solar system passes through interstellar space, the strong magnetic field generated around the heliosphere deflects the charged ions, pushing them out of the way. However, slow-moving neutral atoms are not affected by the magnetic field and penetrate deep into the heliosheath. When this happens, these neutral atoms from the ISM interact with energetic protons (which do have charge) rapidly spiralling along the magnetic field embedded in the solar wind. When this interaction occurs (known as charge exchange), an electron is stripped from the ISM atom and attracted to the energetic solar wind proton, thus making it neutral. When this exchange occurs, an energetic hydrogen atom (electron and proton) is ejected. An ENA is born.
Artist impression of IBEX (NASA)
Now, this is where the clever bit comes in. As mentioned before, neutral atoms do not “feel” magnetic fields, so when ENAs are created they are ejected in a straight line. Some of these atoms will be directed toward the Earth. IBEX will then measure these ENAs and work out where they came from. As they will have travelled directly to IBEX, the location of the termination shock may be deduced. Over a period of time, IBEX will be able to build up a picture of the locations of these atomic interactions and relate them the characteristics of the boundary of our Solar System.
But the best thing is, we won’t need to send a probe into deep space and wait for decades before it traverses the boundary layer, we will be able to make these measurements from Earth orbit. Such an exciting mission. Roll on the Pegasus rocket launch October 5th, 2008!
